I've seen the tippers at weddings I've gone to. What does it get them? Well, if the waiter is assigned 2 tables at 12 people each(Which is usually the case), it usually ensures that tipper gets served first. That water/drinks are replenished without having to ask for it. Simply put, more attentive service. For bartenders, it helps ensure you get prompt service when you go up to the bar.
I'm not saying it's rude or not, I'm just explaining what I've seen it gets you. Most of the weddings I go to are huge affairs in the NYC area, 150+ guests. When the table doesn't give that extra incentive, I can attest that it's harder to find the waiters, whereas when I've seen a tipper at my table, the service is much better.
I agree. I tipped the waiter at the captain's cocktail party for past passengers on the last cruise I was on. It's a huge affair held in one of the bars, and all the drinks (about five different signature cocktails) are complimentary. Upon sitting down and being served our first drink, we passed the waiter a $5 wrapped around a fun-size KitKat. Let me tell you, whenever our drinks got low, another tray was brought around pronto for us to pick from; we probably got four free cocktails apiece whereas most of the non-tipping tables around us received two. We left another $2 on the table when we left as a thank-you.
This sort of party is different from a wedding or a corporate shindig, in that there is no host that's paying the gratuity - the bartenders and waiters were getting their standard cruise payout at the end of the week - so I felt zero guilt for paying for better service. I'm sure there were plenty of passengers who felt that paying a bit for their (otherwise free) drinks was unnecessary - fine for them.
See, I would see trying to be served first as a bit off.
There were probably others at the party that resented our group a little - it's rare to get drinks for free on your average mass-market cruise ship, and if they would quibble over a small tip then they were likely there to get as much as they could for as little as possible. I consider our $7+candy bar (for a table of 4) a small price to pay to get someone to take personal care of us - the waiter that night even remembered who we were when we returned to the same bar a few nights later, no small feat when there are 3,000 passengers aboard.
While I would never presume to tip when someone else is hosting, at a gathering like this cocktail party I would absolutely pay to be served first, promptly and generously.